package org.apache.lucene.index;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;
import org.apache.lucene.store.IndexInput;

final class TermBuffer implements Cloneable {
	private static final char[] NO_CHARS = new char[0];

	private String field;
	private char[] text = NO_CHARS;
	private int textLength;
	private Term term; // cached

	public final int compareTo(TermBuffer other) {
		if (field == other.field) // fields are interned
			return compareChars(text, textLength, other.text, other.textLength);
		else
			return field.compareTo(other.field);
	}

	private static final int compareChars(char[] v1, int len1, char[] v2,
			int len2) {
		int end = Math.min(len1, len2);
		for (int k = 0; k < end; k++) {
			char c1 = v1[k];
			char c2 = v2[k];
			if (c1 != c2) {
				return c1 - c2;
			}
		}
		return len1 - len2;
	}

	private final void setTextLength(int newLength) {
		if (text.length < newLength) {
			char[] newText = new char[newLength];
			System.arraycopy(text, 0, newText, 0, textLength);
			text = newText;
		}
		textLength = newLength;
	}

	public final void read(IndexInput input, FieldInfos fieldInfos)
			throws IOException {
		this.term = null; // invalidate cache
		int start = input.readVInt();
		int length = input.readVInt();
		int totalLength = start + length;
		setTextLength(totalLength);
		input.readChars(this.text, start, length);
		this.field = fieldInfos.fieldName(input.readVInt());
	}

	public final void set(Term term) {
		if (term == null) {
			reset();
			return;
		}

		// copy text into the buffer
		setTextLength(term.text().length());
		term.text().getChars(0, term.text().length(), text, 0);

		this.field = term.field();
		this.term = term;
	}

	public final void set(TermBuffer other) {
		setTextLength(other.textLength);
		System.arraycopy(other.text, 0, text, 0, textLength);

		this.field = other.field;
		this.term = other.term;
	}

	public void reset() {
		this.field = null;
		this.textLength = 0;
		this.term = null;
	}

	public Term toTerm() {
		if (field == null) // unset
			return null;

		if (term == null)
			term = new Term(field, new String(text, 0, textLength), false);

		return term;
	}

	protected Object clone() {
		TermBuffer clone = null;
		try {
			clone = (TermBuffer) super.clone();
		} catch (CloneNotSupportedException e) {
		}

		clone.text = new char[text.length];
		System.arraycopy(text, 0, clone.text, 0, textLength);

		return clone;
	}
}
